attempting to avoid. The causal analysis of restraint represented a new approach to
eating behaviour and the prediction that restraint actually caused overeating was an
interesting reappraisal of the situation. Wardle further developed this analysis (Wardle
1980) and Wardle and Beales (1988) experimentally tested the causal analysis of over-
eating. They randomly assigned 27 obese women to either a diet group, an exercise
group or a no treatment control group for seven weeks. At weeks four and six all subjects
took part in a laboratory session designed to assess their food intake. The results showed
that subjects in the diet condition ate more than both the exercise and the control group
supporting a causal link between dieting and overeating. From this analysis the overeat-
ing shown by dieters is actually caused by attempts at dieting.
ii) The boundary model of overeating In attempt to explain how dieting causes
overeating, Herman and Polivy (1984) developed the ‘boundary model’, which repre-
sented an integration of physiological and cognitive perspectives on food intake. The
boundary model is illustrated in Figure 6.6.
According to the model, food intake is motivated by a physiologically determined
hunger boundary and deterred by a physiologically determined satiety boundary.
In addition, the boundary model suggests that the food intake of restrained eaters is
regulated by a cognitively determined ‘diet boundary’. It indicates that dieters attempt to
replace physiological control with cognitive control which represents ‘the dieters selected
imposed quota for consumption on a given occasion’ (Herman and Polivy 1984: 149).
Herman and Polivy (1984) described how after a low calorie preload the dieter can
maintain her diet goal for the immediate future since food intake remains within the
limits set by the ‘diet boundary’. However, after the dieter has crossed the diet boundary
(i.e. eaten something ‘not allowed’), they will consume food ad lib until the pressures
Fig. 6-6 A boundary model explanation of overeating in dietersEATING BEHAVIOUR 155